To secure an adequate degree of kneading or agitation in the conventional continuous kneader, powder and granular material of the largest amount possible must stay in the kneader, considering limited length and processing capability. To this end the supply of a powder and granular material to be fed to the raw-material-supplying part of the kneader should correspond to its processing capability. An excessive flow of the processed material, which occurs especially around its discharge outlet, also needs avoiding.
Regarding the supply of a constant amount of raw material, a variable-speed, constant-supply device is provided, or a fixed gate is provided to supply the raw material from the top of its casing. Regarding the excessive flow of the processed material, a so-called "return paddle," wherein the feed angle of the paddle is reversed, is provided around the discharge outlet, or a dam gate is provided at its discharge part.
The conventional kneader has drawbacks in that when a self-curing material is kneaded, the kneading efficiency is hindered by the kneaded material that adheres to the paddles and that cures thereon. To solve this problem an apparatus having a self-cleaning effect was disclosed in Japanese Patent Publication No. 62-44969.
However, those remedies proposed above still have some drawbacks. That is, the constant-supply device is expensive. The fixed gate has disadvantages in that its possible shapes are limited since any interference with the rotating shafts and paddles must be avoided, which results in a narrow range of adjustment, and in that it alone is unable to prevent excessive amounts of highly fluid powder and granular material from being fed into the kneading part, which results in an irregular kneading. Additionally, since none of the methods of providing a return paddle and of using the dam gate can completely discharge the processed material in the machine, a problem occurs in that the residual material fixedly adhering to the shafts and paddles hinders the machine from being easily restarted.